Introduction: Nowadays, Imaging of the myocardial perfusion (MPI) using the single photon emission tomography (SPET) in the diagnosis of coronary artery disease, especially myocardial ischemia, is of great importance. In contrast to the coronary artery angiography, MPI is non-invasive, less expensive and more physiological. Unfortunately, this image is affected by the some artifacts. These artifacts lead to decrease image diagnostic accuracy and increase false positive cases. One of the most important effective artifacts is due to attenuation. These attenuation artifacts are caused by the left breast tissue in women, diaphragm in men and the chest wall in both sexes. Because of the inherent non- uniform attenuation map in the thorax region, this problem is very complex. Methods: The aim of this study is to correct attenuation artifact with a simple method that is available and very easy to use. In this study we used transmission scanning by 99mTc in the sequential views and an attenuation map was created. After attenuation correction of the original images with attenuation map, non corrected and corrected images were compared with angiography results to apply attenuation correction based on functional findings. Results: Results show that new artifacts are created and experiences of physicians in the impression of the images is critical. Finally, the sensitivity of images increased from 86.20% to 96.42%, the specificity decreased from 85.71% to 54.54% and the diagnostic accuracy decreased from 86% to 78%. Conclusion: Attenuation correction can produce new artifacts, which can influence the way scans are interpreted. It seems that attenuation correction of the images, need special experience. Lack of enough experience in attenuation correction techniques, can comprise the diagnostic accuracy of images.